Lubricant



3,271,311 LUBRICANT Arnold J. Morway, Clark, and Albert J. Bodner, Linden, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Oct. 8, 1963, Ser. No. 314,630 5 Claims. ((31. 252-39) This invention relates to lubricants, either greases or fluid-s, that will increase in consistency or viscosity upon heating, but upon cooling under slight shearing stress will decrease in consistency or viscosity. Particularly, the invention relates to .a lubricant containing alkaline earth metal salt of acetic acid dispersed in mineral oil and stabilized with a small amount of a low molecular weight polyolefin and metal salt of a high molecular weight fatty acid.

Lubricants of the invention are particularly useful in lubricating gears operating at high temperatures because of their ability to thicken and inhibit leakage from the gear case during operation. On the other hand, convent-ionallubricants decrease in viscosity upon use at high temperatures and are therefore more likely to leak from the gear case during use. At the same time, the lubricants of the invention have good extreme pressure and antiwear properties. Furthermore, these lubricants will not detrimentally chemically react with the gears which is a disadvantage of many gear lubricants containing extreme pressure agents.

In one form of the invention, the lubricant is normally fluid (i.e. at 77 F.) but gels on heating. Now fluid lubricants are known containing oil and alkaline earth metal salt of acetic acid (or acetic anhydride) and intermediate molecular Weight (C to C fatty acid. However, these known fluid lubricants do not exhibit reversible thickening or gelling upon heating. Thus, the present invention represents an improvement over said known lubricants by achieving reversible gelling, which is accomplished by using high molecular weight fatty acid and polyolefin in place of part or all of the intermediate molecular weight fatty acid. Furthermore, the use of high molecular weight fatty acid in combination with the surfactant effect of the olefin polymer can result in a lubricant of good stability and wherein the particle size of the acetic acid salt is very small, e.g. about 2.0 microns.

The high molecular weight fatty acid used in the present invention includes C to C preferably C to C fatty acids. While saturated fatty acids can be used, better results are generally obtained if the fatty acid is unsaturated or is a mixture of saturated and unsaturated acids. Thus, preferred fatty acids will include tallow fatty acids, oleic, palmitoleic, gadoleic, erucic, arachidonic, myristroleic acid, etc. These fatty acids are usually derived from either animal or vegetable sources. In some cases, commercial fatty acid derived from naturally occurring materials will contain both saturated and unsaturated acid. For example, some commercial fatty acids will contain about 40, or even 60 wt. percent of saturated fatty acids, with the remainder being principally mono-unsaturated fatty acid along with minor amounts of poly-unsaturated fatty acid. Trace amounts of lower fatty acid may also be present. These mixed saturated and unsaturated fatty acid materials will usually have Wijs iodine numbers of about 35 to 75, preferably 40 to 70, and saponification numbers of 250 to 150, preferably 225 to 175 mg. KOH/gm.

The alkaline earth metal component of the mixed salt composition of the invention includes calcium, barium, strontium and magnesium, although calcium is preferred. Usually, the acids are neutralized in the presence of the polyolefin with alkaline earth metal base, e.g. a hydroxide,

mite States Patent oxide or carbonate. Lime (calcium hydroxide) is preferred.

The polyolefins are amorphous, i.e. non-crystalline, polymers of monoolefins, e.g. alpha olefins, having 2 to 6 carbon atoms, said polymers having a molecular weight in the range of 500 to 5,000 Staudinger, preferably 600 to 1400 Staudinger. Examples of such polymers include polyethylene, polypropylene, polyisobutylene, etc.

The oil component of the lubricant is preferably mineral lubricating oil, although synthetic lubricating oils such as Ucon oils, ester oil, polycarbonate oil, polysilicone oil, etc. can be used as part of the system.

In general, the lubricants of the invention will comprise a major proporition of lubricating oil and alkaline earth metal salt of about 1.0 to 25.0 wt. percent acetic acid; about 0.1 to 10.0 wt. percent of high molecular weight fatty acid and about 0.2 to 8.0 wt. percent of polyolefin. Normally, fluid (i.e. fluid at 77 F.) lubricants will contain alkaline earth metal salt of about 2.0 to 10.0 wt. percent of acetic acid, about 0.4 to 1.5 wt. percent of high molecular weight fatty acid and about 0.4 to 1.5 wt. percent of the polyolefin.

The metal salt is preferably formed by neutralizing all acid with alkaline earth metal base, in at least a portion of the oil, in the presence of the polyolefin, followed by dehydration at a temperature of about 250 to 350 F. This dehydration is preferably carried out in two stepsthe first dehydration step being on the acid side. This is done by initially utilizing an amount of metal base insufficient to react with all the acid present, e.g. 80 to 99 wt. percent of the base required for complete neutralization is used in this initial stage. After dehydrating on the acid side, the lubricant can be made neutral or slightly alkaline by a second stage reaction involving the addition of a small additional amount of alkaline earth metal base, followed by further dehydration to evaporate the water of reaction of this resulting second neutralization. Good results have been obtained by carrying out the first stage of the neutralization such that the free acidity during the dehydrating step is equivalent to about 0.5 to 3.0 wt. percent as oleic acid, based on the total weight of the concentrate. The second stage dehydration is preferably carried out while the product is neutral or has a slight alkalinity, e.g. 0.05 to 0.3 wt. percent as free sodium hydroxide, based upon the Weightof the concentrate.

Alkaline earth metal salts and soaps of other acids can also be incorporated in the final product, including salts of inorganic acids such as phosphoric acid, nitric acid, hydrochloric acid, etc. These salts and soaps of other acids can be formed during the neutralization steps previously noted, by neutralizing the corresponding acid with the alkaline earth metal base.

Various additives can be added to the usually in amounts of 0.1 to 10.0 wt. the weight of the finished lubricant.

finished lubricant, percent, based on Among additives that can be added are corrosion inhibitors such as'sodiurn' nitrite, lanolin, wool grease stearine; antioxidants such as phenyl a-naphthylamine; auxiliary extreme pressure agents; auxiliary antiwear agents; dyes; etc.

EXAMPLE I Preparation of concentrate A concentrate was prepared having the fol-lowing formulation wherein all percents are weight percents:

Mineral lubricating oil of 80 SUS viscosity at 210 F. 68.4

The oil and most of the hydrated iime were added to a jacketed grease kettle and cycled between said kettle and a Charlotte colloidal mill to form .a smooth, uniform slurry. The tallow fatty acid and polyisobutylene were then added as mixing of the kettle contents continued by passage through said Charlotte mill. Acetic acid was slowly added during said mixing while keeping the temperature of the mixture below 210 F. to prevent boiling by passing cooling water through the kettle jacket. After all the acetic acid had been added, a free acidity determination showed 2.0 wt. percent, based on the kettle contents, as free acidity calculated as oleic acid. The grease mixture was then externally heated to 300 R, which temperature was held for 15 minutes, all the while circulating the mixture through said Charlotte mill. At the end of this time, the free acidity had dropped to about /z% calculated as oleic acid. A small amount of additional lime, as a 40 wt. percent lime slurry in mineral lubricating oil, was added to neutralize the free acidity and to give a free alkalinity as 0.02 wt. percent NaOH. The product was then cooled to 250 P. where the phenylalpha-naphthylamine was added. The product was then further cooled to 100 F. Mixing by passage through the Charlotte mill was continued during the entire process including cooling.

Preparation of finished lubricant 25 parts of the concentrate was mixed with 75 parts of additional mineral oil. The resulting mixture was homogenized to give a smooth, viscous fluid composition.

The formulation and properties of the finished lubricant are summarized in the following table:

Composition (wt. percent):

Glacial acetic acid 4.00 Tallow fatty acid 0.65

Polyisobutylene of 750 mol. wt 0.53 Hydrated lime 2.55 Phenyl a-naphthylamine 0.20

Mineral lubricating oil, 80 SUS at 210 F 92.07

Properties:

Appearance Excellent Visc. at 100 F., SSU 1694 Visc. at 210 F., SSU 94.8 Centrifuge (4 hrs. 1500 rpm), vol. percent solids 0.05 Oven test, 4 hrs. 374 F. Gels 1 4-ball Wear test (1800 r.p.m., kg. load, 1 hr.,

75 C.) 0.23 Water sensitivity, vol. percent solids on centrifuging 4 hrs. at 1500 r.p.m., added water- 1 Soft gel which becomes fluid when cooled under low rates of shear and gels again on heating.

The oven test was carried out by filling an ASTM pour point jar up to its mark, which is about /2 full, with the lubricant. The test lubricant was heated for four hours at 374 F. and then cooled for 45 minutes. The lubricant formed a soft reversible gel during this test. On stirring the cooled gel, with a spatula, it fluidized. On reheating to 374 F. for /2 hour, the fluid again formed a reversible gel. 1

The centrifuge test was carried out in an ASTM centrifuge and the volume percent of separated material was reported.

Water in varying amounts was mixed into samples of the lubricant, fol-lowing which the water-contaminated lubricant was again tested in the centrifuge test. It is seen that as much of 10 wt. percent added water was absorbed by the lubricant without affecting its stability.

What is claimed is:

1. A lubricant having a tendency to increase in viscosity on heating and decrease in viscosity on cooling under low rates of shear, comprising a major amount of lubricating oil and alkaline earth metal salt of about 1.0 to 25.0 wt. percent of acetic acid, about 0.1 to 10.0 wt. percent C to C fatty acid having a Wijs iodine number of 35 to and a saponification number of 150 to 250, and about .2 to 10.0 wt. percent of an amorphous polyisobutylene having a molecular weight of about 600 to about 1400 Staudinger, wherein all of said weight percents are based upon the total weight of the composition.

2. A lubricant according to claim 1, wherein said lubricating oil is mineral lubricating oil, said alkaline earth metal is calcium, and said C to C fatty acid is C to C fatty acid.

3. A normally fluid lubricating oil composition comprising a major amount of mineral lubricating oil, and calcium salt of about 2.0 to 10.0 wt. percent acetic acid, about .4 to 1.5 wt. percent C to C fatty acid having a Wijs iodine number of 35 to 75 and a saponification number of 150 to 250 and about 0.4 to 1.5 wt. percent of a polyisobutylene having a molecular weight of about 600 to 1400 Staudinger.

4. A lubricant according to claim 3, wherein said fatty acid is tallow fatty acid.

5. A method of preparing the lubricant of claim 1, comprising partially neutralizing with alkaline earth metal base in at least a portion of said lubricating oil, said acetic acid and said G to C fatty acid in the presence of said amorphous polyisobutylene, with about to 99 wt. percent of the total amount of alkaline earth metal base required for complete neutralization, heating the resulting mixture to dehydrate the mixture at temperatures of 250 to 350 F., then adding additional alkaline earth metal base followed by again heating to dehydration to form a lubricant ranging from neutral to slightly alkaline.

References Cited by the Examiner UNITED STATES PATENTS 2,810,695 10/1957 Young et al 25239 X 2,833,718 5/1958 Morway et al 25239 2,917,458 12/1959 Morway et al 25239 X 2,935,477 5/1960 Morway 25239 3,098,042 7/1963 Morway et al. 25239 3,112,270 11/1963 Mitacek et a1 25241 DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner. 

1. A LUBRICANT HAVING A TENDENCY TO INCREASE IN VISCOSITY ON HEATING AND DECREASE IN VISOSITY ON COOLING UNDER LOW RATES OF SHEAR, COMPRISING A MAJOR AMOUNT OF LUBRICATING OIL AND ALKALINE EARTH METAL SALT OF ABOUT 1.0 TO 25.0 WT. PERCENT OF ACETIC ACID, ABOUT 0.1 TO 10.0 WT. PERCENT C14 TO C3 FATTY ACID HAVING A WIJS IODINE NUMBER OF 35 TO 75 AND A SAPONIFICATION NUMBER OF 150 TO 250, AND ABOUT .2 TO 10.0 WT. PERCENT OF AN AMORPHOUS POLYISOBUTYLENE HAVING A MOLECULAR WEIGHT OF ABOUT 600 TO ABOUT 1400 STAUDINGER, WHEREIN ALL OF SAID WEIGHT PERCENTS BASED UPON THE TOTAL WEIGHT OF THE COMPOSITION.
 2. A LUBRICANT ACCORDING TO CLAIM 1, WHEREIN SAID LUBRICATING OIL IS MINERAL LUBRICATING OIL, SAID ALKALINE EARTH METALIS CALCIUM, AND SAID C14 TO C30 FATTY ACID IS C14 TO C20 FATTY ACID. 